1. Field of the Invention
The present disclosure relates generally to a multi-operational system for use in petroleum exploration and development. More particularly, the present disclosure relates to a drilling system comprising a peripheral skidding system and/or a removed, lowered, and centrally located setback and racking system to enable a plurality of operations, such as, but not limited to, offline stand building and racking of tubulars, workover, and drilling operations, to be performed concurrently.
2. Background of the Invention
Offshore production of oil and gas requires the use of offshore drilling, completion, and workover rigs. These drilling, completion, and workover rigs are used in different phases of operation for the exploration and production of oil and gas. Offshore rig operations require a vast amount of manpower and the cost of operating these rigs is substantial. The rigs comprise systems for, among other operations, lifting and handling of loads, rotating of tubulars, power generation, circulation of fluids, monitoring of down hole activity, and maintenance of well control and safety.
Conventional systems comprise drilling equipment used in offshore activity for lifting and moving loads, rotating and handling of tubulars (e.g., drill pipe, drill collars, logging tools, casing, etc.), and assembling of tubulars (e.g., connecting multiple pieces of pipe in an end-to-end manner, etc.) prior to lowering the multi-piece unit into the well bore), assembling pipe and equipment, disassembling pipe and equipment, lowering pipe and equipment to the sea floor, and inserting components into the wellbore, and are also used in recovery operations. The systems are also used in drilling, completion, and workover operations.
When drilling operations are conducted in deep water, greater costs and logistical challenges can be confronted relative to operations in shallower waters. A major cost associated with drilling and producing a well is the cost of leasing the platform and associated equipment. Each day of rig time can cost hundreds of thousands of dollars. Accordingly, it is desirable to plan and design drilling operations to operate as efficiently as possible. The increased costs are compounded, for example, by the additional time required to deal with the challenges of operating in deep waters, and the make-up and break-out of tubulars during a drilling operation.
Operations for lifting and moving loads, for rotating and handling tubulars, and for drilling generally occur in the rig floor area. The rig floor area is positioned over the wellbays. Since the standard wellbay design is established in a matrix or grid format (e.g., a 4×4 layout), access to the wellbays below the rig floor is restricted by such designs. Therefore, due to the limited access to the wellbays, such a matrix format typically allows for only a single rig function (e.g., an active drilling derrick/mast, a workover operation, a wireline operation, a coiled tubing operation, etc.) to take place at a time. For example, the running of a drilling riser generally precludes the building of stands on a rig of standard design, thus relegating the first trip into the well bore to utilizing singles for tubulars.
Additionally, to assist the efficient handling thereof, tubulars are typically assembled and stacked vertically in an area within the rig floor known as the setback.
The racking of tubulars in the derrick or mast of the rig may undesirably act as a sail, imparting excessive wind loading forces onto the rig during inclement weather. In gusting wind conditions, for example, so-designed prior art rigs can thus be adversely affected by the resulting dangerous motions and dynamics caused by the impact of the wind on the setback within the derrick or mast. The mass, wind resistance, etc., imparted to the rig by the positioning of tubulars in an elevated setback normally mandates the removal and dismantling of such tubulars during high wind (e.g., hurricane) conditions.
The current industry standard of locating the setback and the derrick or mast within/on the rig floor requires a high level of complexity and automation, and undesirably provides that numerous activities take place overhead of the drilling crew. A serious cause of injury to, or even fatality of, offshore drilling rig workers is the falling of objects dropped from above the rig floor.
Traditionally, offshore wellbores are formed (e.g., drilled and completed) using a single load path (e.g., derrick, rig, drilling assembly), thus mandating that all wellbore tasks (e.g., drilling, completion, stimulations, workovers, etc.) be performed from a single drilling assembly. Recently, efforts have been made to decrease the time required to drill offshore wells by performing some tasks simultaneously. For example, U.S. Pat. Nos. 6,085,851 and 6,056,071 to Scott et al. disclose a multi-activity apparatus and method for conducting drilling operations. In general, Scott et al. disclose a drilling platform having dual drilling assemblies (e.g., separate load paths and/or derricks). In the method disclosed in Scott et al., some activities during the top hole drilling phase and the post drilling phase are performed substantially simultaneously by a main derrick and an auxiliary derrick.
U.S. patent application Ser. No. 12/840,658 describes a method for drilling an offshore wellbore into the seabed from a platform positioned proximate the water surface. The disclosed method comprises making up a first tubular string with a first conveyance assembly and running the first tubular string into the wellbore with the first conveyance assembly, and, while performing a wellbore task with the first tubular string, making-up a second tubular string from a second conveyance assembly, withdrawing the first tubular string from the wellbore with the first conveyance assembly once the wellbore task is completed, and running the second tubular string with the second conveyance assembly into the wellbore. Such a system enhances the speed at which wellbore tasks can be completed, but does not enable multiple wellbays to be serviced simultaneously and limits operations to two activities.
U.S. Pat. No. 4,444,275 to Beynet et al. discloses a carousel for a vertically moored platform. The disclosed carousel rotates about a central support post such that a drilling apparatus can be guided thereby from an anchored drilling vessel or tethered platform above a drilling template placed on the sea floor. Beynet et al. do not address the issues created by positioning a setback on the drilling floor in a drilling rig with regards to safety, wind loading and dynamics associated with the high CG (center of gravity) of the setback.
Accordingly, there remains a need for a drilling system that addresses the significant problems associated with the limitations of a matrix drilling format, the excessive wind loading forces that must be dealt with as a result of conventional racking of tubulars within a drilling rig, and/or improves the safety of workers on a rig by limiting the quantity and types of objects that are elevated and handled above the rig floor. Desirably, such a system provides for improvements in drilling performance, safety, and/or hurricane evacuation response. Improvements in drilling performance can include a reduction in the time required to drill and/or complete a wellbore, for example, by more efficient utilization of the rig floor of a platform rig assembly to enable multiple activities or operations, including exploration and/or production operations as well as completion, testing, workover, and maintenance operations to be performed more efficiently. Improvements in safety and/or hurricane evacuation response can be provided by eliminating the use of or the need for some physical equipment (e.g., a setback located on the rig floor and elevated within a drilling rig) traditionally required to conduct offshore drilling operations. Such an improved drilling system is also desirably more efficient than conventional drilling systems, providing for reduced costs associated with leasing capital drilling equipment, and/or lowered design costs for new drilling rigs.